Synchronization in color television



Dec. 22, 1953 M. v. KALFAIAN SYNCHRONIZATION IN COLOR TELEVISION 4Sheet'sLSh'eot 1 Filed July ll, 1951 .l IIIIIM' I rIIII II IIIIIJ| "IIIIII INVENTOR. ,4.1/

Dec. 22, 1953 M. v. KALFAIAN SYNCHRONIZATION IN COLOR TELEVISION 4Sheets-Sheet 3 Filed July ll, 1951 @www IN V EN TOR. yf-f vg+ nom+ omlo| Dec. 22, 1953 M .v. KALFAIAN 2,663,755

S'YNCHRONIZATION IVN COLOR TELEVISION BLUE AMPLIFIER FROM VIDE 0 TINE DIVID/NG WAVE GATE

GA TE GA re aA T5 130 GATE SYNCH/-Z O/VIZ/NG PULSE-GENERATOR fg. 5 P//A5E Manu/.A TOR 0F sync-Pm s55 INVENTOR.

Patented Dec. 22, 1953 UNITED STATES PATENT OFFICE SYNCHRONIZATION INCOLOR TELEVISION Meguer V. Kalfaian, Los Angeles, Calif. ApplicationJuly 11, 1951, serial No. 236,262

in one mode of operation at the vreceiving end,V

the horizontal synchronizing pulses are separated from the verticalpulses by a local oscillator (operating atline frequency of 15,750cycles per second), both the phase and frequency of which are controlledby the incoming horizontal pulses. While the incoming regular pulses arecapable of aligning the phase and frequency of the oscillatorautomatically, a survey of the operating performance of the existingsets shows that these oscillators must be almost-accurately tuned in`resonance to the above frequency, and be free of frequency drift. Eventhe most expensive sets seem to require such tuning adjustmentfrequently; as from time to time the reproduced picture 4 Claims. (Cl.ri- 5.2)

with a resistance-capacitance network having a peat successively incomplementaryfpairs around the carrier, occupying frequency spacesbetween fcifm, feiZm, ciSfm etc., with gradually climnishing amplitudes.had contained phase modulation, the time-period of each carrier-cyclewould change from normal, and cause effective frequency modulation withcorresponding swing of the sidebands. However, these repeatedrsidebandsmay be narrowed f.

to the first pair by waveshaping thev amplitude rise and fall of eachtime-divided envelope to the simple curve'of the sine-squared function.Similarly, in order to avoid effective frequency modulation, the carrierphase may be shifted stepwise; changing abruptly at the boundaries ofeach envelope; provided that the carrier amplitude is held negligiblylow at the boundaries, so as to avoid sudden transient effect betweenadiacent envelopes of the carrier.

The waveshape of the controlled type of timedivided modulation is shownin Fig. 1, wherein, video signals offtherst primary color are conveye'dover the peaks ofthe time-divided carrier envelopes; the video signalsof the second j primary color are conveyed over phase-advancing of thecarrier wave in every second envelope, as represented by 0 0 0, etc.;and the video signals of the third primary color are conveyed overphase-retarding of the carrier wave in every other`second envelope, asrepresented -by 0 0,'

etc. 'In order to produce the wave in nearly the' ideal waveform, thecarrier is first produced inreduces the amplitude of horizontal andvertical synchronizing pulses below the operating level.

The type of picture synchronization employed herein is contemplated tobe used in conjunction with the system of color television, disclosed inmy Patent No. 2,558,489, June 26, `1951. The :system described utilizesydouble sideband modulation of a time-divided carrier wave, withsimultaneous amplitude and phase modulation for multiplexing compositesignals of the color images. Also, in order to avoid widely expandedsidebands that are usually associatedw'ith abruptly interruptedtime-divisions `of the carrier wave, in conjunction with phasemodulation, special waveshaping of the carrier envelopes is `employed inthe system. To explain this waveshaping condition briefly, it is shownthat when the carrier is interrupted abruptlyk at a time-dividingfrequency fm, and the modulation frequencies varied ,maximum to jm/2,the s idebands would redependently in two separate channels, as at B andC, and both the phase angle of the carrier. and waveshape' of theenvelope are presynthe` sized, ineach channel by sampling method, and

finally combined to obtain the wave asshown at A.

VIn order to utilize greater effective time of signal transmission,there is disclosed in the above mentioned patent a color-sequenceswitching system, whichreverses the normal color sequence at randomelemental intervals, depending upon vwhich of the second and thirdprimary colors is present for transmission. For example, in all colortelevision systems, itis assumed that each image element will contain amaximum number of three primary color components. If it were the casethat everyone of the image elements had contained all the primary colorssimultaneously, then the time allotted to convey these components in'any color-system would be utilized at the maximum efficiency. However,such is not the case in color images, and in the major part of one imageframe, the majority of ele- Similarly, if the carrier mental images willcontain only one or two primary colors. Hence, the time allotted forconveying the missing primary colors will be completely wasted, andresult in poor image definition. In order to utilize most of the timeallotted for conveying the three primary color components, advantage istaken of the fact that, simultaneous amplitude and phase modulation willprovidez three`way.;'selectivityA of'ftlie; video.A

signals, forexample, by assigning amplitude mod--` ulation to conveyVideo components of the Green color; assigning phase modulation of thecarrier wave in backward direction to conveyfvideo com-.-

ponents of the Blue color; and assigning phases:

modulation of the carrier wave in forward direction to convey videocomponents"opting-Redcolor. Then. .by employing a colore-sequence re.-vversing switch, the sequence of video components of the Blue and Redcolors may be changedeat any random elemental scanning interval, to

transmit whichever; color"corriponentV isU present at? that: time.. Of4course-,1,w1'ren:v duringa-f, timeelement .bothgthei Bluefand.R'edftcolorsyare Difes-- ent.: and equally; important color; value,lthen; the? colon component assigned-toe that-,time-ele-- mentyvillbegtransmitted- InA orderrto; simplify;- detectionof; the: phase,-

modulated.' signals; without thenecessityof. a. reference carrier:A at.the; receiving; end,.. a; novel i method-of phase modulation had Vbeendescribed inthe'fabove mentioned patent; wherein, phase:- angle'. ofi,the carrierfin each; succeeding time-- division is'l shiftedrepresentative' of, inteliigence, by a; difference-anglevmeasurablefrom4 a; preceding angle,l whereby, each; preceding phase.

tioni representing: the; vertical: and; horizontal.

sync pulses; For: even-line..8 retrace,;` the:v carrier.: phaseisfshifted t degreesfbotlrinforward@andi verticale directions;sequentiallyfrom; envelope to; envelope,-representing.simultaneous;verticalL and.;

horizontalisyncpulses: Thefphase.fdiscrirninated` sync: pulses arethenseparated fromzthe video: signals by amplitude selectors, which may beanyof 'the conventional types;` Itlmay b`e= addedihere that;r the systemwill operate lon' any-type of 'interlace' withoutnecessitating-'changes' orme-adjustmentI of anyV circuitl components;snce'- the' system" is Y independent`l of:l locallyA generated; Waves;orytuning of any circuit. Such a condition will providev pictureswithoutjitter` or waves.. Similarly, due. to, the.. simultaneous.. color,system.. there, will be no. line crawl, ,and the.. picture. will`havegood color. texture.

Having, described. the. various: aspects;4 of., the. inyention, theefollowingspecification will be der voted sto. .the detailsV oioneftype.of apparatus,fthat.j

may be femployedl in connection .withzV the; invention;Infthefdrawings.:

mitted carrier envelopes, and the steps in which the carrier envelopesare produced.

Fig. 2 illustrates a block diagram of the transmitter for video signalmodulation.

Fig. 3 illustrates how the carrier wave is phase modulated to representsynchronizing pulses.

Fig. 4 illustrates a phase discriminator circuit for separating thevideo and synchronizing signais?V lo Fig. 5 illustratesfrpartlyafblockdiagram of the synchronizing signal modulator in connection with thetransmitter in Fig. 2.

Eig, 6.. illustrates the type of synchronizing pulses that" are employedto phase modulate the l5 carrier wave.

Sim'zeL the2pizesent invention is to be used in conjunctionL with` themodulation system described in my aliove mentioned patent issue, partdescription: of same is included herein in order to clarify thesubstance thereof.

Modultedwaveshape ofjthe carrier wave The` modulatedwaveshape'of thecarrier wave is^^shownzinFig 1; atA, Inorder to adhere t0tir'efconditions inzwhich-thesidebands are limited*v to'- restricted?regions, IT have described by tlieoryinA my` abcve.- mentioned'v patent.issue, that.

the lwaveshape of4 amplitude risev and fall at the -hounda'riesofndividualfcarrier-envelope be that otl the: sine-squaredf'function: nottoexceed the timel periodf tm, and that the carrier phase in eachVenvelope. be in `alsteadystate Step from boundary tozh'cundary;Similarly, in order to avoid-sudden-phase shiftsoffthe carrier wave in352 dynamics Condition. ieislpessenuaithat the carrier'power level-:atfthe boundaries of each envelopeT he.` zero; o'r negligibly low, wherebythe carrier phase-'-inleachtenvelope'may be diierent from the others,without causing. delaying action 40-of phase resolution between the twophases of the-carriers Such faniideaLor nearly ideal waveshape .of-F the1 carrier Waver envelope is produced inperiodic-fsteps; as illustratedat B to E inclusive.

'- The: carrierwaveiisproduced@inV two separatechannels-,1andtlieioutputs yof=these two channels are=gatedzin alternatasequenceat the time dividing frequency; .whereby duringV the quiescentperiod'.` of :each: channel the" carrier vwave may be 5c.' waveshapediand simultaneously amplitude and phasel modulated; byf-sampling-.methodand final- 1y., the. periodic outputsof'f the-twouchannels are combinedfor naltransmission; For example, at the output?` of* the rst channelthe periodic 5i@carrier#envelopesiatBareaproduced, and at the output: ofthe fsecond'- channel' the periodic carrierfenvelopeseat'lCfareproduced.Then by combining'the periodicV carrier envelopes at BandC,'.the.f.desirediwayeform as:shown at A is o'cce.- tained; Thepea-leiamplitudes ofthe periodic en- Velopes .of t the 4carrierVwavezatfB' are determined by the steady" state sampled: voltages shownat D; and; tlief peak: amplitudes-'f of? the: periodic envelopes ofthecarrierwave ati: C` are determined byithe5steadyfstatesampledvoltages shown at E.

For` full detail of the"y simultaneous amplitudeand.l phasemodulator;in" conjunction with the color-'saquenceswitch, reference-may be made toEig. 1:y illustrates the waveshapeaof the transf-752myfabovefmentionedlpatentiissue. However, the

ascenso following description in connection with the transmitter blockdiagram in Fig. 2 will be suicient to explain the function of thesystem.

In Fig. 2, the carrier wave is produced by two independent low Qoscillators I and II, both of which oscillate at the carrier frequency.The phase angle of oscillation I is shifted by video signals of the Blueprimary color arriving from source I in phase-modulator 2, and the phaseangle of oscillation II is shifted by video signals of the Red primary'color arriving, from source 3 in phase-modulator 4. The phase modulated oscillation of I in modulator 2 is appliedY upon the oscillatorII through the gate 5, and the phase modulated oscillation of II inmodulator 4 is applied upon the oscillator I through the gate 6. Thesegates consist of ordinary gridcontrolled vacuum tubes, and their grid tocathode voltages are so biased that they are normally renderedinoperative, in order to normally prevent the oscillatory voltages ofoscillators I and II acting upon each other for phase shifts. Block 'irepresents a generator of the switching wave at frequency fnl/2, and itdelivers alternate positive voltages upon the gates 5 and 6 for theiroperation in alternate sequence, so that oscillators I and II shift thephase angles of each others oscillation in alternate intervalsv (at timedivision frequency fm), by angles (representing signals of the Blue andRed primary colors) measurable from phase angles that the oscillationsof oscillators I and II resolve in immediate preceding intervals, Forexample, assuming that during one positive half-cycle Wave period offnl/2, the gate 5 is operated and the oscillatory voltage of oscillatorI is admitted to shift the phase angle of oscillation of oscillator IIinto an iii-phase relation, the shiftedl phase of oscillation of IIrepresents the normal phase of oscillation arriving from I in additionto the phase shift that represents the video signal of the Blue primarycolor. This operation reverses during thefollowing positive half-cyclewave period of the switching generator 1, which at this time operatesthe gate 6 and the oscillatory voltage of oscillator II (phase modulatedby the signals of the Red primary color) is applied upon the oscillatorI to forcefully shift its oscillation into an in-phase relation. Thus itis seen that the output oscillations of oscillators I and II shift insteady state steps periodically with respect to each other by anglesrepresentative of the video Blue and Red primary colors measurable frominfinitely changing reference angles of the carrier wave. To distinguishbetween the video signals of Blue and Red primary colors, the

phase modulator Z is arranged to retard the car-Y rier phase ofoscillator I, and the phase modulator 4 to advance the carrier phase ofoscillator II.

For combined phase and amplitude modulation, the periodic steady statephase modulated portions of the oscillations of carrier oscillators Iand II are further amplitude modulated in steady state steps by thevideo signals ofA Green primary color from source 8. The original videosignals of Green primary colors from v'source 8 are sampled inAlvi-samplers 9 and I periodically (as shown at D and E in Fig. 1) inphase with the steady state phase modulated portions of the oscillatorsI and II, so that these periodic portions are simultaneously amplitudemodulated -in the IM-modulators II and I2, by the video Green signals.Thus, the outputs of modulators'V II Vand I2 contain simultaneousamplitude andv phase modulated carrier, in alternate steady state stepscillations are modulated .in steady state steps,

and alternate envelopes of the carrier wave appear across the platetanlrcirouits of these tubes, which are then mixed in block I'I, toobtain the carrier wave -in the form as shown at A in Fis. `1. Y

For colorswitching, the signals of video Blue color retard the carrierphase, and the signals of video Red color advance the carrier phase,whereby'these color'signals may be automatically selected'atrthereceiving end. For color-sequence switching, auxiliary gates* I8 and I9,and phase modulators 20 and 2|A are employed. The output of.oscillator`Ibesides being phase modulated by the-norma1lyassigned video componentsof Blue color, it is also phase modulated in auxiliary modulator 20 bythe video Vcomponents of the Red color. Similarly, theoutput ofoscillator II besides being phase modulated by the normally assignedvideo components of Red color, it is also phase modulated in auxiliarymodulator 2I by the video components of y Blue color. When thevideo'components of both Blue and Red colors are-present, theseauxiliary-gates are inoperative, and the image components` of Blue andRed colors are transmitted inregular sequence. However, when during anelemental scansion period one of these colors 'isabsent, or below anegligible magnitude, the normally assigned gate becomes inoperative and"the'auxiliary gate operates, so that theother color component istransmittedinstead; thus utilizing most all of the elemental scansionperiodsof transmission, which otherwise would be lostk in regularsequential transmission.' Y

Phase 4 modulated sync pulses In the drawing of Fig. 3,"there is shown awaveform of the time-divided .carrier envelopes, wherein, the time areasYa. are devoted to the conveyance of video signals; and the time areas bare devoted t the conveyance of synchronizing pulses. In `vthe firstsectionof areas b, the carrierv phase is-shifted degrees backward inevery succeeding envelope; representing the horizontal synchronizingpulse. Inv the second section of areas b,the carrierv phase is shifted90 degrees forward in every succeeding envelope; representing the`vertical synchronizing pulse; for oddline. And in the (third lsection ofareas b, the carrier phase is shifted backward 'and forward se-vthadot-and-daShedline c,.n.lg;. 3.. When the..

carrier. envelop'sfare- .thus limited in. amplitude, the. output.A willbe .(disregardingthe. narrow dips between'. the envelopes); as if the.carrier were of constant. amplitude,A .and that the phase angle wereshifted abruptly in; time-division steps. ThisI type of phaseYmodulation isv detected. by the discriminator circuit given nFig. 4.

Fig. 4theincomingcarrier wave is passed through the R. F;.stag e shownbyblock 22; passed through the.. I. F. stagespshown by block 23; passedthrough'` .am amplitude. limiter, or multiple thereof. lin the: usualmanner, shown by the. block: 24.;- and the output: is.. applied .uponthe amplilier; tube V. Due to the resistance R in the anode circuitof,this tube, .the I. F. voltage in this circuit will follow the abruptphase changes of: the input I. F.. voltage faithfully. Whereas in the.reactive: circuit Ll .the value of Q' is so adjusted that, the timerequired for phase res olntion from one abrupt state toanOtheris oneenvelope-period. Accordingly, at. the beginning of. each carrierenvelope-there will vbea. phase difference of the I. F. voltage. betweenR and LI, whichl isi av function of the original intelligence. These.phase differences of: the I. F; voltages may thenbe'discrimina-ted,asgfollows :I

The coupling of the secondary coil L2 is adj usted slightly less than;the value of critical coupling, whereby' the voltage in the secondary isin; quadrature with .respectto the primary coil Ll. The diodes Vl andfV2 are connected to theY terminals y and y.' of.' coil L2, in: a mannerthat, the output voltagesacross Rl'v and R2 are the differences of therectified'outputs. of the individual diodes. When thervoltage across- Ris applied upon the resistance R3, as shown, then the rectied output.voltages across RI. andRZ will vary with variation `ofthe phase anglebetween voltages across R and` L2, That is, when the voltage-phaseacross R and L2 Vis inquadrature, the outputvoltages. acrossRvl1 and R2are of equal and constant amplitude. Whereas,v when the voltage-phaseacross@ L2. shifts such that, the positive half -cycles across. B3 add`to ther positive half-cycles at y, by greater amount than at y', thenthe rectified voltage across RI will be greater than the voltageV acrossR2. And when the positive half-cycles across vR3v add tothe positivelhalf-cycles at y' `by greater amount than at y, then. the rectifiedvoltage across R2 will be greater than the voltage .across Ri. Thus,selective voltagesV across Rl and R2 may be obtained by shifting thecarrierphase, forward or backward, from envelope to envelope at thetransmitting end. For com-pleteselection of the colorvideo signals, thevoltages across RI 'and R2 are further rectied by diodes V3 and V4, the.out-- puts of which are independentlyA amplified vfor iinal color-imagereproduction, as 'shown in the drawing. Actually however, the diodes V3and V4 are not necessaryy if the vdeo amplifiers are of theresistance-capacitance coupled type, as only ther positive signalsacross `RI and R2 are utilized in exciting the normallyr cut-off biased'controly grids of` the-tri-.eolor :image reproducing tube.

and Blue primary .oolorsfwill vary within a ivre-A determined limitofamplitude, whereas beyond this amplitude-limit, the pulses are derivedby independent amplitude. selecting circuits forv synchronization. andbeamf-blanking. The amplitude selecting circuitsv are not shown in thedrawing, .as they are .conventionally employed in monochrome sets, andany one of the types is suitable for the Purpose.

Phase modulator of sync pulses Fig. 5 is av modification of the blockdiagramA in. Fig. 2,. VIn the arrangement of Fig. 5, only phasemodulation is. included for simplicity of drawing. The. twooscillatorsof the carrier wave. arerepresentedloy the blocks I and II. The out--puts of thesev oscillators are split in phase degrees by thetransformers. Tl and T2, and applied independently upon the controlgrids of phase modulator tubes V5, V6 and V1, V8. The cathode biasY ofmodulator tube Vt is so adjusted that the. tube normally operates at itsmaximum.

applies upon the oscillator II, in the same phaseA angie as itoriginated inV the oscillator I. When. the positive video Red signalarrives at the control grid of cathode'follower and phase inverter tubeV9, the video signal is applied upon the second. control grid of V5 inpositive polarity, and upon the second control grid of V6 in negativepolarity. In this manner, the transconductance of tube V5 isincreased,and the transconductance of tube V6 is decreased, withv the result thatthe phase angle of the oscillation I in transformer T3 is shiftedforward in its application upon the oscillator II. Since as .describedin the foregoing, that the maximum phase shift allowed for signalmodulation is 72 degrees, the minimum transconductance adjustments of V5and V6 are substantially above zero, and the phase shift in thetransformer TilY is other than 90, so that with zero video-signal theoscillation I is applied upon the oscillator II in the same phase as itoriginates in oscillator I. |Ihe operation of phase modulator tubes V1and V8 is similar to the operation of V5 and V5, and the output isappliedv upon the oscillator I in the same manner, and therefore, itneeds no further eX- planation. In this case however, the video Bluephase modulated oscillation of II retards the phase angle of oscillatorI, by reason of the inverted connection of transformer T2.

The output oscillation of oscillator I after b eing phase modulated'. bythe Red video signals, itis applied upon the oscillator II, through gate25, While the output oscillation of oscillator II after being phasemodulated by the Blue video signals, it is; applied upon the oscillatorI, through gate 26. The gates 25 and 25 are .Oherated, in alternate.time periods by the alternate positive; Yhalf-cycle voltages of thetime-dividing wave produced in block 2. For the video-signalmodulation,r the output of oscillator I (at op)` contains periodicsteady-state phase modulations. representative of the video Bluesignals,

and the output of oscillator II (at op) contains periodic steady-statephase modulations representative of the video Red signals; in sequencewith respect to each other.

The synchronizing pulses are generated in positive polarity at theoutput terminals X, X

and X of block 28; in the form as shown in Fig. 6. Simultaneously withthese pulses, there are produced pulses in negative polarity, asindicated at the extreme end terminals of block 28, which are appliedupon the gates 25 and 23 to render them inoperative, and prevent thesignal modulation from interfering with the pulse modulation. The gates29, 39 and 3i, 32 are normally rendered inoperative, and are so arrangedthat, they operate only when simultaneis applied upon the inputs ofgates 29 and Si simultaneously. The output voltages of gates 2Q and 3Dare phase inverted by the blocks 33 and 34, so that when the gates 29ands@ are operated alternately by the simultaneous synchronizingpositive-pulse from block 28 and alternate half-cycle positive-voltagesfrom block 2l, the oscillations of oscillators I and II will be advancedin phase by 90 degrees in every succeeding half-cycle periods of fm/Z.The outputs of gates 3l and 32 are applied in phase upon the oscillatorsI and II, so that when the latter gates are operated, this time theoscillations of oscillators I and II will be retarded in phase by 90degrees in every succeeding alternate intervals of the wave fnl/2. Ifhowever, when the pulse generator applies a positive pulse upon gates 30and 3l simultaneously, then the oscillation of oscillator II passingthrough gate 3l retards the phase angle of oscillation of I, and theoscillation of oscillator I passing through gate 30 advances the phaseangle of oscillation of oscillator II; causing sequentialphase-retarding and phase-advancing of the carrier wave from envelope toenvelope. In this case, and with reference to the phase discriminator inFig. 4, both the vertical and horizontal scannings are acted uponsimultaneously, foreven-line field scanning.

Sequencev of sync pulses The distribution sequence of horizontal andvertical pulses is shown in Fig. 6. At PI, both the vertical andhorizontal pulses at X are pressent simultaneously (by way ofcross-connection in the block diagram), for even lines. From this pointon, the horizontal pulses P2 at X continue. Between the last two pulsesP3 and P5 of the even-line field, the vertical pulse P4 is produced atX"; for odd lines. From this point on the horizontal pulses continue,until at the last horizontal pulse P6, where both the horizontal andvertical pulses appear at X, for a new start of the even-lines.

- The synchronizing pulse generator 28 is shown in block diagram, aspulse generators are commonly known and practiced in the television art,and the sequence of pulses may be obtained by known methods andcircuitry.

, While I have indicated in the foregoing specification that the type ofsynchronization described herein is intended to be used in conjunctionwth the type of video modulation employed in my above mentionedinvention, it is obvious that other types of video modulation may alsoutilize the system. For example, the type of modulation described hereinmay be utilized in conjunctionwith the vestigial sideband transmissionsystems only during the transmission of sync pulses. The time period ofeach envelope may also be much longer than described in the foregoing.Similarly, the general principle of this invention indicates that,numerous substitutions of parts, adaptations and modifications arepossible without departing from the spirit and scope thereof.

I claim: f

1. In color television where amplitude modulation of the carrierwave isassigned to convey video signals of the first primary colorcontinuously; phase modulation of the carrier to convey video signals ofsecond and third primary colors sequentially, and where synchronizationof the projected positions of elemental image.

. components at-the receiving end with that `of the transmitting end isestablished by way of' transmitting discrete signals distinguishable onefrom the other for the determination of time positions of the horizontaland vertical retracings, the system of transmitting discrete signals forthe attainment of' said synchronizationV which comprises: means toproduce carrier oscillation in rst and second channels, means to applythe output oscillations of the first and second channels uponl eachothers input oscillations periodically at a time-dividing frequency rateessential to convey video signals of any of the three primary colors, inav sense that, the output oscillation of each is capable of shifting theothers input oscillation to an in-phase relation periodically insequence by force, means to shift the phase angle of the carrieroscillation periodically in the rst and second channels in rst o'rforward direction by vdeo signals of the second primary color byrepresentative angles limited to in those periodic intervals when one isshifting the others phase angle, means to shift the phase angle of thecarrier oscillation periodically in sequence with the second primarycolor in the said rst andsecond channels in second or backward directionby video signals of the third primary color by representative angleslimited to 1L', in the preceding manner, means to modulate the amplitudeof the carrier oscillations in the first and second chan'- nels inalternate sequence at saidtime-dividing frequency rate by Video signalsof the iirst primary color, means to produce a first pulse at the timeperiod when the horizontal scanning is to fly back for retrace, means toproduce a sec,- ond pulse when the vertical scanning is to iiy back forretrace; namely for even-line eld scanning, means to produce a thirdpulse'when both the horizontal and vertical scannings are to fly backsimultaneously for retrace; namely for odd-line scanning, means to shiftthe carrier phase by the rst pulse in the first and second channels by amaximum angle X in the said first or forward direction in alternatesequence at the time-dividing frequency rate,. means to shift thecarrier phase by the second pulse in the iirst and second channels by amaximum angle X in the second or backward direction in alternateVsequence in time phase with thevlast said modulation, means to shiftthe carrier phase by the third pulse in the rst andsecondchanaseeondfor'xforward:andshackwand dlireetlen Seequentially, in:.'alternatelinteryals ;of, the time -dif,vitiing..frequency, end meansttozcnmbine those sequentiallymeriodie. portions rofstherontnut s--Gilletinsidnrinswhiehitheyrnroeeedrto shiitzthe phaseangle ordineochers input -oscillatinn, :.wherebyiin y,each itimefiiivisionpi thecarrieror kperifxief thereof the :carrier 'amplitnde .-GQntans :Video`-zinformation Vof .the irst .primary :color: `the phaseLa-ngleitoailimitfrin theirstnr fOr-- .mardidirectionicontains ,Yideojniormation,Qi the second aprirnary.A color sthe.: phase; angle to a limit a: inthe secondfor backward1directionfeentains video information of the thirdprimary icolor; fthe maximum phase angle Xin lthe first 4or forwvardl.direction v.c cnitains ghorizontal synchronizing'.j information;.=,themaximum phase angle X lindzhe.second,onloaclrward `directioncontains4vier- -ljsical y.synchroniaing inormation; :namely for reyenelinefrieid scanning; Vtand :sequential fmax- Y mum phase .angles X iin theinrst. and second or irorwardfand backward directions @contain .simu-Yitarieouseh.oriznntal.and vertic-a1fsrnchronizine informations.

2. In timeediyided @olor televisionY Where-amvfplitude modulation of,ithe. :carrier .Ware :is asafsiened sto convey. -izideo :signalent-the,first YPr- A@mary color .continuouslw phase, modulationfof theearrierwavelhy representatreaneles limited to :rizo 4normen avideo signals A ofsecond and vthird primary colors 'seeuentiallrfzand Where synchronizingrsignals .are ,transmitted via phase :moduilation zby ainoaxlnllnil anglerofwfthecarrier iwave, a phase -imodulatingqapparatns v'for theseemnositeisignals whiehzoomprises: `first-,and sectond .oscillators.-ofsubstantially a .Single Y Car- .'rierahferequeney, viirst Land .secondlphase. modelaaors. and .frirst zandsecond znonnally inoperative gates:associated therewith, @so cross-,coupled beftween ,thetfirst,andfseeond oscillators that, each #oscillatoraiterlbeing.phaseemodulated:1S 92tpahle pf., shifting :thev zot-,hersphase angle. to an in-phase .irelation-ithrough1-eits. rassociatedfilete when seperated, ,sonroesnpr videosignals and meansgtherefpr:to-.phase ;m91l11a18.=,1ih.f1`sil and esenondeosoillators independentlyin the 'first and second `phase modulators by representative an- -gies'cimiteri tom, aswitehms-fwevesoume and therefor no operate. the. rstnd:Second vvgatesalternaiely eliminate ,positiyejvoltages .at a:times-'dividing @frequency essential to` convey video signals, wherebythe first endsewnd 9S- .;-cniatorsisniftieacheothers Aphase:arlilf's`vil@ fab tornate 'sequenceiby Een;'resentative angles ,limited to inrstand `second phase-shiitersand arend. fanatica-rin normally .incoerentegates associated therewithisoprossecoupled between 'the inst fandsec-omi.osoillatorsthat each oscillator after passing:through-litsrespective.AphaseQshifter Jandoate, Whenfonerted, shiftstheothers phase angle doy ansa-ingle aloaclvva rd direcation, .riifth@and Sixth gates and first and second 180 ...phase-,inverters.,assooiated, therewitnso press-.coupled,hetmeenrthenrst and second `os-;cillators.; .in series i Vlfiththe Said irstfiand fsee- -ondphaseeshifters that, -eaeh oscillator after passing through itsrespective phase-shVijrter; 180 ,phase-inverter;` zandfeate whenoperated, shiftssthe others phase Vby an angle X in forvrawarddirection, -nieans .to fapply the switching Wave in A:alternate:positivepoiarities npon the third; Y fith fand lionrjzh sixth gates in suchmagnitudes that the :gates are rendered just rsnort of operation, meansto produce a first pulse at the .angles X in backward direction.representing horizontal synchronizing information, frneanslto apply thevsecond kpulse Aupon the nfth and. sixth gates in positive polarity :forl operation; ,and .'.smultaneously 1upon the first and second gates.negative polarity for non-operation, whereby the first -and secondA.iscillators .shift each Aothers Vphase angles in acontinuous steps ,by.angles .Xlin forward direction representing vertical synchronizinginformation, ,means .to .apply'the third V-pulse upon odd gateasuchas.the third and Iith gates simultaneously-in positive polarity ,foroperation; and simultaneously upon ,the Iiirst and second 'gatesinnegative polarity for non-operation, 'Wherebyfthe rst and-secondoscillators shift each-others Eplflases'by angles X inbaek- `ward andforward directions-in sequential steps representing simultaneous`horizontal andV vertical .synchronizing informationsand ,-rne'ans 'to.combine the outputs of ,the iirstand second 0s- -cillators inthe"manner describedforliinal 'transmission. Y Y l y 3. VIn colortelevision Wheream'plitde :modula- -tion of the carriervwave .isassignedto convey video signalsrof the first v:primary v colorcontinuously, phasel modulation-vof the .carrier 'to .convey v`videosignals of second and third primar-y colors sequentially, -ajnd `Where*synchronization of --the PTQjeted positions, of elemental v.iinaogge.components `:at vthe;receijvfing .end with that ofthe transmittingfiendlsvestalolished byway .of ltransmitting .discretesignalsdistinguishable A.one from the lother for thedeterrnination .of .timepositions tof the l`hor'iz'ontalandizerticalretraeings, 'thesystem of:transmittingcompositedsignals Aof syn- .chronization vand videocomponents, .all'ldistinguishable:one from the other, WhichncompisesY'envelope:in successive steps in-nrstor derivar-didi- 'rectionby an.angleX representative of fthehori- :zontal synchronizing signal,- eachof said-snccessive steps 'being'measurable from-a Lpreceding step,whereby 4.eachpreceoling step-represents a .reference angletoiasncceeding step, for-dtection purposes; 'means jior shifting phaseangle vor the .carrier from Aenvjg'alope ktoenvelope -irf aforesaidmanner in second or, backward Y.direction"loyran angle X ,representative:o'f the LVertical 'synchronizing signal, 'namely' "for v teven-lineretraeing; .means for :shifting'phase angle -o'f the carrier inv.preceding manner Valternately vfrom Venvelope `to envelope in firstand .second directions-representative of Ythe verticaly synchronizingsignal, nainely for odd-.line .retracingv nieans'or shiftirigi'gnhaseangle of the carrier in every 'second"suecei'edini.r

envelope, in aforesaid manner, in first or forward direction by angleslimited to :c representative of video signals of the rst primary color;means for shifting phase angle of the carrier in every other secondsucceeding envelope, in preceding manner in second or backward directionby angles limited to :c representative of video signals of the secondprimary color; amplitude modulator means and means therefor to shift thepeak magnitudes of said carrier envelopes, in the manner described,representing video signals of the third primary color, whereby compositesignals representing synchronization and video components are alldistinguishable one from another; and means for transmitting thecomposite modulated carrier wave to the receiving end.

4. As set forth in claim 3, which includes in combination means forreceiving said transmitted carrier wave; means for deriving first signalfrom said phase modulation X of the carrier in said first direction, forthe control and operation of said horizontal retracing; means forderiving second signal from said phase modulation X of the carrier insaid second direction, for the control and operation of said verticalretracing,

namely for even-line retracing; means for deriving simultaneous rst andsecond signals from said alternate forward and backward phasemodulations X of the carrier, for simultaneous control and operation ofsaid horizontal and vertical retracings, namely for odd-line retracing;means for deriving video signals representing the rst primary color fromsaid modulation a: in forward direction; means for deriving videosignals representing the second primary color from said phase modulationin backward direction; and means for deriving video signals representingthe third primary color from said amplitude modulation, for the controland operation of lappropriate color-image reproducing device by saidderived first, second and third video signals, thereby attaining saidsynchronization of video signals at the receiving end with that of thetransmitting end.

MEGUER V. KALFAIAN.

Name l Date Chatterjea Apr. 3, 1951 Number

